A fast heart rate (100 beats per minute or faster in an adult). This can be compared to bradycardia which is an unusually slow heart rate, usually signified by a pulse under 60 beats per minute. Additional Info: Tachycardia can be caused by exertion, strenuous exercise, emotions, hyperthyroidism (overactivity of the thyroid gland), disease, injury, heart disorders, or exposure to certain drugs or chemicals. Ventricular tachycardia refers specifically to tachycardia that is initiated in the ventricles of the heart. You may have heard the slang "V-tach" used for this condition on medical television shows such asE.R. Supraventricular tachycardia is initiated in the area of the heart above the ventricles and is sometimes abbreviated SVT. There are many additional subtypes of tachycardia, but these are beyond the realm of focus here (MSDS's and related safety documents). See: Further Reading below for more information. MSDS Relevance: This term usually appears on an MSDS as a symptom of chemical exposure. However, an abnormally fast heart rate could be due to chemical exposure, a heart attack, or simply a panic attack, among other causes. Read the MSDS's of the chemicals you work with so you know if they can affect the heart rate or body chemistry. If you ever experience an unusual heart rate be sure to seek immediate medical attention. See also: Bradycardia, Palpitation